Shoe stiffener and method of making the same



Patented Oct. 1, 1940 UNITED sTATEs SHOE STIFFENER AND METHOD OF MAKING THE SAME Richard Almy, Lancaster, Pa., assignor to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania No Drawing. Application April 27, 1938, Serial '1 Claims. (01. l2146) This invention relates to shoe stiffeners and, more particularly, to box toes and box toe material carrying a suitable stiffening compound which is adapted to be softened or tempered by 6 the application of heat, so that in the lasting operation in the manufacture of shoes, the blank is molded about and takes the shape of the toe end of the last, and on cooling retains such shape.

Heretofore, shoe stiifeners have been formed by saturating or impregnating a fibrous base with an emulsion of resin, wax or ,the like, intermixed with a rubber solution. Such emulsions are extremely viscous, even when the resin or wax con- 15 tent thereof is as low as ten per cent, and are not satisfactoryfor use as stiffening compounds since the high viscosity results in failure to effect more than ah incomplete or partial saturation of the fibrous base. Various attempts have been made a to reduce the viscosity of such compounds by adding water to thin the emulsion. This practice reduces the viscosity of the solution and permits saturation to be effected; however, when the saturated base is dried, the amount of dry stiff- 1 ening material carried by the base is so small that the material is unsatisfactory as a shoe stiffener.

A shoe stiffener should be hard, resilient and flexible so that it will impart to a shoe a maximum degree of firmness and yet not be brittle, so that when subjected to a deforming pressure, it will resume its original shape upon removal of the pressure. A stiffener should adhere to adjacent parts of a shoe to form a unitary structure but such adhesion should not be accompanied by staining. To fit in-the rapid routine of modern shoe manufacture, stiffener blanks must be adapted to be tempered or rendered soft quickly, and when in such condition, they must be capable of being wiped" over or lasted with little effort on the part of the operator. In order that a shoe will keep its shape, the stifiening material in a blank should be resistant to temperatures ordinarily encountered in store windows and wear. A satisfactory stiffener need possess the above mentioned desirable qualities and still be so economical in cost as to permit its universal application to all types of shoes.

This invention has for its chief object to ob- 50 viate the disadvantages inherent in previous shoe stifieners and the method of making them. An object of my invention is to provide a shoe stiffener which possesses not only inherent properties of stiffness, rigidity, flexibility and resilien- 55 cy when cold, and of being made limp or plastic comprises dispersions of substantially neutral resins, waxes, bitumens or other water repellant substances or mixtures thereof, in which rubber latex, or rubber dispersions, is dispersed. Such stiffening agent is so prepared that a homogeneous mixture is formed having a melting or softening point at a moderate temperature, between 175 F. and 185 F., which is not injurious to the leather components of a shoe and which sets rapidly when cooled. A bibulous foundation or base, such as felt, paper, cotton flannel or canvas duck, is impregnated with the stiffening agent, and formed into shoe stiffening blanks of appropriate size and shape.

In order that my invention may be readily understood, I will describe a preferred embodiment thereof. A satisfactory stiffening compound can be made by the following formula:

Parts by weight Cumar resin (128 C.) dispersion (60%)---- 100 Crude montan wax dispersion (60%) 100 Rubber latex (38%) 100 In the preparation of the stiffening compound, the dispersions are formed by grinding the resin and the wax in water by means of a ball mill for a sumcient time to divide them in minute particles ranging from one micron to perhaps thirty microns in size and averaging about seven microns. The resin and wax dispersions may be prepared separately or together, as desired. The dispersions so made contain approximately 60% of resin and/or wax. Such dispersions are only temporarily stable but may be used if continuous stirring is carried on. Preferably, approximately twelve parts by weight of stabilizing agents such as the sodium salt of iso-propyl naphthaline sulfonic acid known commercially as Aquarex F," are added to stabilize the dispersion. It will be appreciated resin or wax dispersions so made contain a high percentage of the dispersed materials without causing the dispersion to be viscous.

The resin and wax dispersions are added to the latex and thoroughly mixed therewith so that the latex is dispersed uniformly throughout the compound. If desired, pigment fillers may be added tothe compound. In such case, I may use a zinc oxide dispersion prepared in the same manner as the resin or wax dispersions. The compound so-made may be used immediately or placed in air-tight cans until it is required for use.

The bibulous base or foundation is saturated or impregnated with the stifiening agent by passing a web of the material through a saturating tank, the excess saturant being removed by drawing the web through squeeze or pressure rods or rolls. The web is then dried by placing it for thirty minutes in a stove or oven heated to approximately 250 F., the stiffening compound being deposited in the interstices of the web and on the surface thereof by evaporation of the aqueous vehicle. Box toe blanks of a desired size and shape are then died or cut out of the web; and are skived to form thin or tapered edges. Such blanks are resilient, tough, rigid and flexible when cold, and are capable of being rendered easily moldable by the application of heat. They are not friable and the thermoplastic material does not powder or give off dust when the blanks are skived or bent.

When it is desired to assemble a shoe, the box toe blank is heated at moderate temperature, roughly, F. to F. depending upon the melting point of the thermoplastic agent and is thereby rendered soft and flexible so that it may be drawn and molded in the pulling over and bed lasting operation. When the molded box toe has set, it is again resilient, tough, flexible and hard and is able to resume its shape after a deforming pressure thereon has been removed. It will be understood it is essential that substantially neutral resins or waxes, such as cumar resin, Montan wax, or mixtures thereof, be used, otherwise coagulation of the rubber particles of the latex will occur when the stiffening compound is formed. If the thermoplastic constituents of the stifiening compound are acidic the rubber particles of the latex will be coagulated during formation of the compound and thus prevent complete saturation of the foundation in the manufacture of shoe stiffeners. It will be appreciated the resiliency and flexibility of the stiffeners arise from the rubber particles deposited in the interstices of the foundation and on the surface thereof. Other types of rubber dispersions may, of course, be used in place of latex.

This invention provides a shoe stiffener which is hard, resilient and flexible so that it will impart to the shoe a maximum degree of firmness and yet not be brittle, so that when subjected to a deforming pressure it will resume its original shape upon removal of the pressure. When inserted in a shoe it will adhere to adjacent parts thereof to form a unitary structure but such adhesion is not accompanied by objectionable staining. It may be tempered quickly and is capable of being lasted with little effort on the part of the operator. It is economical in manufacture and does not require excessive expenditures in machinery for commercial production.

The term dispersion is used herein to denote a suspension of minute particles in Water.

In my copending application, Serial No. 204,607, filed April 27, 1938, I have disclosed a shoe stiffener comprising a base material impregnated or saturated with a homogeneous mixture of latex, casein and acidic resins, and I do not claim such types of stiifeners except as they form the subject matter of the application for Letters Batent v hereinbefore identified.

mo-plastic stiffening compound, said compound consisting of a homogeneous aqueous dispersion of a substantially neutral thermo-plastic material chosen from a class consisting of substantially neutral resins, waxes, or bitumens, and rubber in which said thermo-plastic material is present in the form of minute particles ranging from one micron to thirty microns in size, and precipitating said particles thereby depositing stiffening compound in the'interstices of the web and on the surface thereof.

2. As an article of manufacture, a normally stiff, resilient shoe stiffener blank adapted to be rapidly rendered soft and plastic by the application of moderate heat, comprising a readily permeable fibrous base carrying within its interstices and on its surface the dried residue of a homogeneous aqueous dispersion of a substantially neutral thermoplastic material chosen from a class consisting of substantially neutral resins, Waxes or bitumens, and rubber in the form of minute particles, to which a stabilizing agent has been added to protect the thermoplastic particles against precipitation while no protective agent has been added to protect the rubber particles against coagulation, said thermoplastic material being present in sufficient quantity to impart to said stiffener plasticity under the application of moderate heat, and said rubber being present in an amount less than the amount of thermoplastic material yet being present in sufficient amount to enhance the resiliency and flexibility of the stiffener while substantially maintaining the thermoplasticity thereof.

3. As an article of manufacture, a normally stiff, resilient shoe stiffener blank adapted to be rapidly rendered soft and plastic by the application of moderate heat, comprising a readily permeable fibrous base carrying within its interstices and on its surfaces the dried residue of a homogeneous dispersion consisting of particles of cu mar resin, particles of Montan wax, rubber latex, and a sodium salt of iso-propyl naphthaline sulphonic acid, suspended in water, said cumar resin and said Montan wax being present in substantially equal amounts and in sufficient quantity to impart to said stiffener plasticity under the application of moderate heat, and rubber being present in an amount less than the amount of ctunar resin yet being present in sufficient amount to enhance the resiliency and flexibility of the stiffener while substantially maintaining the thermoplasticity thereof.

4. In the method of making a normally stiff, resilient shoe stiffener adapted to be rapidly rendered soft and plastic by the application of heat, the steps consisting in impregnating a readily permeable fibrous web with a thermoplastic stiffening compound, said compound consisting of a homogeneous aqueous dispersion of a substantially neutral thermoplastic material chosen from a class consisting of substantially neutral resins,

erate heat, the steps consisting in impregnating a web of readily permeable fibrous material with a thermoplastic stiffening compound, said compound consisting of a homogeneous aqueous dispersion composed of particles of cumar resin, particles of Montan wax. and latex to which a stabilizing agent has been added to protect the particles of cumar resin and Montan wax against precipitation while no protective agent has been added to protect the latex against coagulation, and drying the impregnated web thereby precipitating said particles and depositing stifi'ening compound in the interstices of the web and on the surfaces thereof.

6. A base fabric adapted for the manufacture of normally stiff, resilient shoe stiffener blanks comprising a readily permeable fibrous base carrying a homogeneous aqueous dispersion of substantially neutral thermoplastic material chosen from a class consisting of substantially neutral resins, Waxes or bitumens in the form of minute particles, and rubber latex, to which a stabilizing agent has been added to protect the thermoplastic particles against precipitation while no protective agent has been added to protect the rubber particles against coagulation, said thermoplastic material being present in said dispersion in the form of minute particles ranging from one micron to thirty microns in size and being adapted to be deposited in the interstices of the base and on the surface thereof by evaporation of the aqueous vehicle, said latex being present in an amount less than the amount of thermoplastic material.

7. As an article of manufacture, a normally stiff, resilient shoe stiffener blank adapted to be rapidly rendered soft and plastic by the application of moderate heat, comprising a readily permeable fibrous base carrying within its interstices and on its surface the dried residue of a homogeneous aqueous dispersion composed of particles of cumar resin, particles of Montan wax, and rubber in the form of minute particles, to which a stabilizing agent has been added to protect the cumar resin and Montan Wax particles against precipitation while no protective agent has been added to protect the rubber particles against coagulation, said cumar resin and said Montan wax being present in suflicient quantity to impart to said stiffener plasticity under the application of moderate heat, and said rubber being present in an amount less than the amount of said cumar resin and Montan wax yet being present in sufficient amount to enhance the resiliency and flexibility of the stiffener while substantially maintaining the thermoplasticity thereof.

RICHARD ALMY. 

